1. Technical Field
The present invention relates to optical element in which a partially reflective layer and a reflective layer are laminated with a substrate interposed therebetween, a manufacturing method of the optical element, an optical device and a display apparatus that uses the optical device.
2. Related Art
Optical elements such as luminous flux diameter enlargement elements have a structure in which a reflective layer is provided on both sides of a laminated body in which a light-transmissive layer and a partially reflective layer are alternately laminated, and the reflective layer is provided on both sides of the laminated body in a lamination direction. According to such elements, it is possible to enlarge the luminous flux diameter of incident light in a direction in which the light-transmissive layer and the partially reflective layer are laminated (refer to JP-A-2006-301234).
However, a specific configuration example is not disclosed in the configuration that is disclosed in JP-A-2006-301234, and if the configuration that is shown in FIGS. 7A and 7B is adopted, intervals between reflective layers (the partially reflective layer and the reflective layer) that are adjacent in the lamination direction differ from one another. More specifically, a luminous flux diameter enlargement element 10D that is shown in FIGS. 7A and 7B includes a laminated body 15 in which a light-transmissive layer 12 and a partially reflective layer 11 are alternately laminated, and includes a first reflective layer 13 and a second reflective layer 14 on both sides of the laminated body 15. In addition, the luminous flux diameter enlargement element 10D includes an incidence surface 16 and an emission surface 17 on both sides in a direction T that intersects a lamination direction S, and a luminous flux L10, which is incident to the incidence surface 16 from an oblique direction, proceeds in the direction T, which intersects the lamination direction S, while repeating total reflection by the first reflective layer 13, total reflection by the second reflective layer 14, transmission through the partially reflective layer 11, and reflection by the partially reflective layer 11, and is emitted from the emission surface 17 in a state in which the luminous flux diameter in the lamination direction S is enlarged. In order to manufacture such a luminous flux diameter enlargement element 10D, a light-transmissive substrate 128 (the light-transmissive layer 12), on which the first reflective layer 13 is formed on a first surface 128a, and a plurality of light-transmissive substrates 129 (the light-transmissive layer 12), on which the partially reflective layer 11 is formed on a first surface 129a, are respectively laminated toward the same direction as the lamination direction S of the respective first surfaces 128a and 129a using an adhesive layer 18. In addition, among the plurality of substrates 129, the second reflective layer 14 is formed on a second surface 129b of a substrate 129, which is positioned on a side that is opposite to the substrate 128 in the lamination direction S.
However, in the configuration that is shown in FIGS. 7A and 7B, the intervals between the first reflective layer 13 and the partially reflective layer 11, and the respective partially reflective layers 11 are equivalent, but the interval between the second reflective layer 14 and the partially reflective layer 11 differs from the intervals between the first reflective layer 13 and the partially reflective layer 11, and the respective partially reflective layers 11 as a result of the adhesive layer 18 not being present. Therefore, optical path lengths of pathways that are followed when incident light proceeds toward the emission surface 17 differ. As a result of this, as shown in FIG. 7C, there is a problem in that peaks and bottoms of phases deviate in each ray of light that follows each pathway and is emitted from the emission surface, a light intensity is weakened, and therefore, unevenness occurs in an optical intensity distribution of emitted light.